Accident avoidance technologies at emergencies, such as an automatic emergency brake and a collision avoidance system, are becoming common. Further, systems that raise caution of drivers and the like for avoiding accidents have also been developed. For example, in Patent Literature 1, a judgment is made on whether a bicycle traveling in front of own vehicle is apt to fall over on the basis of weather information and road information read out from a database. In a case where the bicycle in front is apt to fall over, a warning to that effect is made to a driver (paragraphs [0043] to [0049] etc. in specification of Patent Literature 1).
In addition, Patent Literature 2 describes a judgment apparatus capable of judging a road surface state (dry road/snowy road/wet road etc.) on the basis of reflected light from a road surface detected by a road surface sensor. In this judgment apparatus, the road surface state is judged on the basis of a signal intensity of the reflected light in addition to a reflection intensity of a horizontal polarization component and vertical polarization component of the reflected light. Accordingly, it is possible to accurately judge notify a driver of the road surface state (paragraphs [0007], [0024] to [0032], etc. in specification of Patent Literature 2).